Electrical switch



Oct. 28, 1958 w. J. SCHULTZ ET AL ELECTRICAL SWITCH H 6 Sheets-Sheet 1Filed Dec. 30, 1955 Invemors William J. Schuhz Carl F. VanBennekom m4 5%Their AHorney 1958 w.,.|. SCHULTZ ET AL 2,858,385

ELECTRICAL SWITCH I Filed Dec. 50(1955 I e Sheets-Sheet 2 ors illicm J.SchuHz rl F Van Bennekom Aa;{ Their AHorney w. J. SCHULTZ ETAL 2,858,385

Oct. 28, 1958 ELECTRICAL SWITCH s Sheet s- Sheet 3 Filed Dec. 50, 1955Fig.

Their Atro W. J. SCHULTZ ETAL Oct. 28, 1958 ELECTRICAL SWITCH .6Sheets-Sheet 4 Filed Dec. 30, 1955 Fig.6

I lnveMors:

William J. SchuHz Carl E VonBennekom by, 4

,4 4 Their AHorney Oct. 28,

Filed Dec. 50, 1955 w. J. SCHULTZ EI'AL ELECTRICAL SWITCH e Sheets-Sheet 5 lnvenrors: William J. Schuhz Carl F. VcmBennekom Their AHor neyOc't- 1958 w. J. SCHULTZ ETAL 2,

ELECTRICAL SWITCH 6 Sheets-Sheet 6 Filed Dec. 30, 1955 United StatesPatent ELECTRICAL SWITCH William J. Schultz and Carl F. Van Bennekorn,Lynnfield, Mass., assignors to General Electric Company, a corpo rationof New York Application December 30, 1955, Serial No. 556,583

6 Claims. ((ii. Nil-27) The present invention relates generally toelectrical switches and in particular relates to an improved electricalswitch capable of handling realtively high circuit loads and havingnovel arrangements for reliably separating the switch contacts in theevent such contacts become welded together upon closure thereof.

In the use of electrical switches for controlling electrical circuits inwhich relatively high current flows, it is relatively common for theswitch contacts to become welded together during the closure of theswitch. For example, in the case of an electrical circuit including atungsten filament load drawing a current of 35 amperes, it is notunusual for the switches to have an inrush current traversing theircontacts at the moment of closure as high as 8 or 10 times the normalload current in the circuit. Thus, it is possible that a current as highas 350 amperes could traverse the switch contacts in which event it isnot unusual for the contacts to become welded together during closurethereof.

If the contacts become welded together, there is no problem inconnection therewith so long as the switch remains closed. However, whenit is necessary to open the switch, particularly in those instanceswhere the switch is a part of an automatic time switch normallyunattended and relying upon a timing motor to provide the necessarypower for opening the switch, it is extremely important that thecontacts open when required. If they are welded together and cannotopen, great damage could occur and the switch would be totallyineffective and unreliable as a circuit controller.

In,the past and in connection with switches having their contactscarried by deflectable spring members, it has been the usual practice toobtain separation of the con-- tacts by storing sufiicient energy in thespring blades during closure thereof so that the stored energy can beused to break any contact welds and thus allow the contacts to open. Inthe case of a switch rated for 35 amperes tungsten load, it has beenfound that a force of 20 ounces must be available in each contactcarrying member to break any welds encountered during the use of theswitch. Obviously the energy required for separation of the contactsmust be stored in the deflectable spring member each time the contactsare closed whether or not a weld occurs at any particular instant ofclosure.

In the case of a single-pole, double-throw switch, a total of 40 ouncesmust be stored in the contact carrying members each time the contactsare closed and, in a like manner, for a double-pole, double-throwswitch, a total of 80 ounces must be stored in the contact carryingmembers at the time of closure thereof.

In order to store the aforementioned large amounts of energy in thedeflectable spring members, it has been found that such spring membersmust be deflected to a considerable extent upon closure of the switch,resulting in very high bending moments which produce high stresses andsevere wearing on the spring members, as well as other parts of theswitch. Moreovenin the case of a time switch having a timing motor forthe source of its actuating power, the motor must be able to develop therequired high level of energy which, of course, results in high loadingin the motor.

It has been found that in relying upon the energy stored in the contactcarrying members for separating welded contacts, there are oftenpractical limitations that prevent the use of this type of switchactuation without adding materially and significantly to the complexity,size and cost of the resultant switch. Moreover, it has beendemonstrated that separation of the contacts resulting from the energystored in the contact carrying members causes the contacts to physicallypull apart from each other, which effect, over any extended period oftime, will ultimately completely deteriorate the contact surfaces.

Therefore, it is a primary object of this invention to provide new andnovel means for separating contacts of an electrical switch that mayhave become welded together during closure of the switch.

It is another object of the invention to provide simple and effectivemeans for separating contacts of a switch that may have become weldedtogether during the closure of the switch wherein the loading of thecontact carrying members has been substantially reduced.

It is yet another object of the invention to provide novel contactseparating means for a switch that may have its contacts welded togetherupon closure thereof wherein the forces for separation are developedonly as required and with a consequent reduction in the size of anypower source utilized to effect switch operation.

It is still a further object of the invention to provide novel contactseparating means for a switch that may have its contacts welded togetherupon closure thereof wherein the welds are separated without anyresultant deterioration of the contact surfaces.

In one aspect of the invention the improved electrical switch comprisesa pair of electrical contacts adapted to move reciprocally relative toeach other to open and close the contacts and mounted on a pair ofclosely spaced deflectable contact carrying spring blades. The bladeshave corresponding inner ends anchored to a fixed support and havecorresponding outer ends free to move relative to each other forcooperation with a suitable switch actuating mechanism that produces therelative movement of the blades which causes the switch to open andclose. A timing motor is utilized to drive the bladeactuating mechanismand this motor functions to deflect the spring blades relative to eachother to cause the contacts to close.

After the contacts have been closed and some time prior to opening, thetiming motor operates to further drive the blade actuating mechanism sothat the blades are further deflected relative to each other to causethe contacts to move transversely relatively to each other. Thistransverse action produces a shearing force across the face of thecontacts and in the event the contacts have become welded duringclosure, the shearing force so developed will effectively break thewelds and permit the contacts to readily open.

All of the energy required for breaking the weld is furnished by thetiming motor and is only furnished by this motor when so required. Inthis way, the switch could function for a prolonged period of operationwithout overloading the motor or the switch itself if no welds occurduring such a period of operation.

in the case of those switches utilizing energy stored in the contactcarrying members for weld breaking. It is true that when there is aweld, the timing motor has an addi-- tional load imposed thereon, but ithas beenfound much more practical and less costly to use a smaller motorcapable of handling intermittent high loads than to use a larger motorthat is continuously loaded at all times.

The objects of the invention together with the benefits and advantagesattendant thereto will be more fully understood upon reference to thedetailed description following, particularly when taken in conjunctionwith the drawingsannexed hereto in which:

Figure 1 is a front view of a program timing device embodying theimproved electrical switch forming the subject invention;

Figures 2 and 3 are partial end views of the programming device shown inFigure 1 illustrating the manner in Whichthe programming dial functionsto select alternate switchpositions;

Figure 4 is an exploded view of the programming device shown in Figure 1taken fromthe rear thereof;

Figures 5, 6, 7 and8 are similar views of the programmingdevice shown inFigure 1 taken from the front thereof'with a number of parts removed toshow a single-pole, double-throw switch associated with the programmingtimer and which functions in accordance with the teachings of thesubject invention, each view showing a different relative position ofthe switch.

Referring now to Figure 1, the programming timer device comprises a mainsupporting plate 9 having an electrical switch terminal block 11'secured to the bottom thereof by means of suitable screws 12 andon whichis carried the rotatably mounted programming dial 13. The dial 13 ismounted in any convenient manner and is arranged to be driven by a geartrain coupled to a timing motor afiixed to the rear of the plate 9. Onthe face of the programming dial, there is a 24-hour clock scale 14surrounding which is a series of spaced radial slots 15 which areprovided to removably receive a plurality of switch position selectors16 which, as shown in Figures 2 and3, are in the form of key membersthat have their inner ends inserted through the apertures 15 andextending within the radial slots provided in an annularsupportingmember 17 located behind the programming dial and spacedtherefrom. The selectors 16 have inner and outer projections 18, 19respectively, intended to cooperate with the inner ends of a pair ofswitch actuating cranks 21, 22 pivotally mounted on the rear of plate 9and'having their inner ends extending through a suitable aperture in theplate. referred to asthe o crank, whereas the crank 22 may bereferred-to as the on crank. As is shown in Figure 2, the selector 16has been pushed downwardly so that its projection 18'will cooperate withthe crank-21 to lift it as the selector-moves relative thereto. InFigure 3 the'selector is-shown in its alternate horizontal positionwherein its outer projection 19 is in a position to cooperatewith the oncrank to lift it as the selector moves relative tothe inner end of thecrank.

Thus, the selector in either position will cause a limited pivotalmotion of the cranks, the particular crank actuateddepending upon theposition of the selector.

An indicating pointer 23 may be conveniently mounted on the programmingdial to cooperate with the clock scale and function as an indicator oftime.

The arrangement described so far is in all respects similar to thearrangement shown and described in the copending application in the nameof Ralph M. Manning, filed December 27, 1954, Serial No. 477,903,entitled, Timing Mechanism, and issued April 29, 1958, as U. S. PatentNo. 2,832,408, assigned to the same assignee to which the subjectapplication is assigned. For a further description of this portion ofthe pro graming timer, reference'will be had to the aforesaid copendingapplication.

Turning now to Figure 4, attention is first called to the cylindricalmember 24 shown on the rear of plate 9 and this member is the sealedrotor and gear reduction unit forming a part of the well known Telechronsynchronous The crank 21 may be convenientlymotor, the remainder ofwhich has been omitted in the interests of clarity since such motors arewell understood by those skilled in the art. The posts 25 on oppositesides of the member 24 serve as mounting arrangements for the motor. Apinion protrudes from the inner end of member 24 and extends through theplate where it engages the gear train utilized to drive the programmingdial 13.

The cranks 21, 22 are pivoted about a stud shaft 26 and are biased bymeans of the springs 27, 23 respectively i such that the inner ends ofthe cranks are urged downwardly relative to the selectors 15.

A pair of slides 29, 31 are mounted for limited sliding motion in thegrooved posts 32, each of the slides having notches 33 at its oppositeedges surrounding grooves in the posts 32 and functioning as stopslimiting motion in either direction transversely of the plate.

A driving arm 34 is pivotally mounted on slide 29 and has its pivotshaft 35 extending through slide 29 to lie within the notch 36 providedin slide 31. The outer end of arm 34- has a flange portion 37 extendingthrough an aperture 38 provided in plate 9 and a spring 39 is providedto bias the arm 34 upwardly along the plate.

Mounted on the rear of switch terminal block 11 are a plurality ofcantilever spring blades 41, 42, 43, 44 and 45 having their inner endsrigidly secured to the terminal block by means of similar base sections46 and having their outer ends freely movable relative to each other andadapted to carry similar electrical contacts 47. The base sections 46have been shown fully in Figure 4 only in connection with blade 41, theothers being cut away or only partially shown in the interests ofclarity. Such base sections comprise the bottom strip 46:: having itsouter end turned up to form the outer mounting flange 46b adapted tooverlie the terminal block 11 at the front thereof, and its inner endturned upon along one of its edges to form the blade 41 on which isformed the inner mounting flange 460. The inner flange an is adapted tooverlie the terminal block at the rear thereof, and both of the flangeshave suitable apertures 46d aligned with apertures in the terminal blockto permit the base sections to be securely attached to the terminalblock by means of rivets 4oe or. the like. The blades and theirassociated base sections are thus formed as a single piece and, if

desired, the blade portion may be ribbed to give added ruggedness tothis part of the switch.

The tips of the blades 41, 43and 44 are notched and.

are intended to lie within the notches 43, 49. and 51 provided in thelower edge of slide 31 and in a like manner the tips of blades 42. and45' are notched and are intended to lie within the notches 52', 56provided in the lower edge of slide 29. All of the blades are biasedtothe left of the plate 9 as viewed in Figure 4, which, in the absence ofany restraining force on the slides 29, 31, will carry both of theslides to their extreme left position within the grooves of the posts32. An auxiliary biasing spring adds further bias in this direction forslide 29.

A steeply inclined cam 53 is attached along the upper edge of slide 31by suitable screws 53a or the like for cooperation with the transverselyextending pawl 54 The arrangement of parts described so far, exceptforthe configuration of cam 53, is similar to the mechanism shown anddescribed in the copending'application filed December 20, 1955, SerialNo. 554,201, in the name of Manning et al., entitled, Time Switch,issued December 10, 1957, as U. S. Patent No. 2,816,184 and assigned tothe same assignee to which the subject application is assigned. For amore detailed description of this portion of the programming timer,reference will be had to the aforesaid Manning et al. copendingapplication.

The switches mounted on the terminal block 11 and intended to becontrolled by the programming device may mechanism for the switch,including the slides and steep cam 53, has been devised to produce apositive shearing action prior to opening of the contacts such that anywelds formed between the contacts are easily separated.

As an indication of the effectiveness of the switch, it

is to be noted that the Underwriters Laboratories requirements for aswitch rated at 35 amperes tungsten load call for 6000 successfuloperations at the rated load. The switch forming the subject inventionhas been successfully operated at 50 amperes tungsten load for as manyas 7800 continuous switch operations without once having switch failurebecause of welded contacts, and there is no reason to believe that weldsoccurring at even higher currents (on the order of 100 amperes) couldnot be effectively separated in accordance with the teachings of thepresent invention. The manner in which the shearing action effectivelyseparates any contact welds will be best understood upon reference toFigures 5 and 8 inclusive. Thus, in Figure 5 the switch blades 41, 42,43 are shown as forming a single-pole, double-throw switch and theposition of the switch is such that the contacts on blades 42, 43 areclosed and contacts on blades 41, 42 are open. The driving arm has movedupward to its normal position adjacent to the lower end of crank 21 andthe pawl 54 is resting on the upper edge of cam 53. In this position, itis possible that the contacts carried by blades 42 and 43 have becomewelded together. In this position of the switch the ofl? crank 21 willbe ineffective to cause switch actuation, but the on crank 22 whenactuated by one of the selectors on the programming dial 13 will movethe driving arm 34 to the left as viewed in Figure 5, carrying with itboth of the slides through the interconnection of the driving arm shaft35. It is well to point out here that the designations on," off havelittle meaning in connection with a single-pole, double-throw switch,but since the terms are helpful in describing the action of the switch,it is believed that continued use of these terms is in order.

The next position of the switch is shown in Figure 6 illustrating therelative positions of the switch blades after the blades have beendriven to the left by the arm 34. Both of the blades 43 and 42 have beenfurther deflected relative to each other and in so doing, their contacts47 have moved transversely relative to each other to develop a shearingforce which effectively separates any welds therebetween. The contactscarried by blades 41 and 42 are open in this position of the switch.

Upon further motion of crank 22, the slides will be moved togetherslightly further to the left in which event the pawl 54 drops off of cam53,'disengages the driving arm 34 from crank 22, holds the slide 31 andlets the slide 29 return to its original position under the drivingforce furnished by the biasing action of spring blade 42. The slideshave thus been moved relative to each other and this position of theswitch is shown in Figure 7 wherein the contacts carried by blades 42,43 are now open and those carried by blades 41, 42 are now closed. Hereagain, the contacts that are closed may become welded together and it isnoted that in this position of the switch, crank 22 is ineffective tocause actuation since the driving arm is held out of engagementtherewith by pawl 54.

The next switching action will be under the control of selectors 16 thathave been set in the off position to cooperate with the off crank, andwhen the program-"1 ming dial moves such a selector to so cooperate withcrank 21, the crank will be rotated clockwise as viewed in Figure 8 andattempt to lift its pawl out of its holding position. However, as isseen in Figure 8, the slope of cam 53 is such that the cam surfaceinterferes with the normal lifting action of the pawl, and the pawl mustpositively drive the cam 53 out of its path before it can be lifted toits normal position on top of cam 53. In so driving cam 53, the blade 41is deflected further toward blade 42, carrying with it blade 42, whichin turn is also deflected to the left, the relative deflecting actionbetween the two blades creating a transverse mation of the contactscarried thereby relative to each other such that a shearing force isdeveloped to separate any welds formed between the contacts. Since theblade 43 also deflects to the left, the contacts carried by blades 42and 43 will remain open during this phase of switch operation.

Upon further actuation of crank 21, the pawl 54 will ultimately clearthe cam 53, thus permitting the switch to return to the position shownin Figure 5.

From the above, it is seen that for either set of contacts mounted inthe single-pole, double-throw switch, there is a positive shearing forcedeveloped just prior to opening of these contacts. Moreover, theshearing force so developed is quite substantial in view of themechanical advantage derived from the arrangement of the blade actuatingmembers relative to the blades. That is, the relatively small forceapplied transversely to the tips of the blades to cause a relativelylarge deflection thereof will result in a relatively large force appliedtransversely along the face of the contacts to cause a relatively smallweld separating transverse displacement of the contacts.

Since the contact blades are securely mounted on the terminal block,being literally wrapped around the edge thereof and having the inner andouter mounting flanges riveted together through the block, and, further,since the blades themselves are sufliciently rugged, being ribbed foradded strength if so desired, the shearing force de- Of course, if thereare no contact welds produced, there will be no shearing forcesdeveloped and, the contacts will simply slide relative to each otherupon actuation of the switch. In other words, the shearing force is only.developed when required to separate welded contacts,

and for this reason, the switch components are not continuously loadedduring operation thereof, but only when necessary to separate welds.

With the arrangement described above, and in the case of a single-pole,double-throw switch, it has been found that for normal operation of theswitch, and in the absence of any welds, the timing motor will have tofurnish a force of approximately 4 ounces to the contact blades when thecontacts are closed, such 4 ounces being sufficient for maintainingproper contact pressure- In contrast, if the switch were functioningsuch that any contact welds were to be separated by pulling forcesdeveloped by energy stored in the blades upon closure of the contacts,it has been found that the timing motor would have to furnish a force ofapproximately 40 ounces to the contact blades each time the contacts areclosed, whether or not any welds result upon closure.

Therefore, under normal conditions of operation and without any weldsoccurring upon contact closure, the loading on the blades and the timingmotor has been reduced to one-tenth of the normal loading required whenthe blades themselves must function to separate contact welds.

Of course, as and when welds occur, there is a momentary increase in theloading on the timing motor and the blades, but such increased loadingcan be adequately handled with the use of a smaller motor and lessrugged blades than would be required were the loading present for eachclosure of the switch contacts. That is, if the blades themselves musthave energy stored therein to separate contact welds, it would benecessary to use a substantially larger motor and 'more rugged blades toachieve a switch life that is comparable to the switch life achieved.with the present invention.

In other words, the timing motor and the switch blades, together withother associated structure utilized in accordance with the teachingsherein could probably be adapted to providevweld separations by the useof energy stored inthe blades, but in such event, the switch wouldrapidly wear out because of the continuous sustained loading thereof.

It is thus an inherent advantage of the present invention to provide asmaller and less rugged overall switch design than was heretoforepossible to handle currents producing contact welds upon closure of theswitch, resulting' in a smaller, more compact, and substantially lesscostly switch.

As has been demonstrated above, the shearing action provided to separatecontact welds is effective for any combination of switch blades, fromthe simple singlethrow arrangement to the more complex double-throwarrangements, with single or. plural poles.

Moreover, although the invention has been illustrated in connection witha switch forming a part of a programming timer, it is to be understoodthat the invention is not limited in its application to suchanarrangement, it being capable of use with any time switch having ablade actuating mechanism similar in principle to that shown anddescribed. Furthermore, although the switch has been shown herein with apair of relatively movable slides provided to cause deflection of theblades, it is to be understood that other forms of blade deflectingmembers could be used so long as the force of deflection is appliedsubstantially transversely relative to the tips of the blades, and thatsuch deflection can be effectively utilized to produce a shearing forcethat will separate contact welds.

Therefore, while a particular embodiment of the subject invention hasbeen shown and described herein, it is in the nature of descriptionrather than limitation, and it will occur to those skilled in the artthat various changes, modifications, and combinations may be made withinthe province of the appended claims, and without departing either inspirit or scope from this invention in its broader aspects.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electrical switch including a pair of electrical contacts adaptedto move reciprocally relative to each other to cause closing and openingof the contacts, a pair of contiguous deflectable cantilever springblades on which said contacts are mounted, corresponding inner ends ofsaid blades being fixed and corresponding outer ends of said bladesbeing free to move relative to each other, means movably engaging saidblades at said outer ends comprising a movable member adapted to move atsubstantially right angles to said blades to deflect said blades and thecontacts mounted thereon and having associated therewith holding meansfor. restraining said movable member after said electrical contacts aremoved thereby to a closed position, said movable member havingassociated therewith switch actuating means operating after closure ofsaid contacts and just prior to opening thereof to move said bladeengaging means to deflect one of said pair of blades toward the otherblade and then away from said other blade to cause said contacts to movetransversely relative to each other to shear any weld producedtherebetween upon closure thereof.

2. The timeswitch as defined in claim 1 wherein said switch actuatingmeans includes a cam member in operative connection with saidimovablemember and a relatively movable switch actuator adapted to provide incooperation with said cam member said holding means and to provide thesaid relative blade movement through movable engagement therebetween.

3. An electrical switch including at least two electrical contactsadapted to move reciprocally relative to each other to cause closing andopening of the contacts, at least two contiguous deflectable cantileverspring blades on which said contacts are mounted, corresponding innerends of said blades being fixed and corresponding outer ends of saidblades being closely spaced from each other and free to move relative toeach other, said contacts being mounted on said free ends, a pair ofmovably mounted members each engaging at least one corresponding tip ofsaid free ends of said blades and adapted to move relative to each otherand at right angles to said free ends to deflect one of the bladestoward one other to cause two of said contacts to close, and drivingmeans including a timing motor for moving said blade engaging members,said driving means operating after closure of said contacts and justprior to opening thereof to further deflect said one of said bladestoward the other of said blades to cause said contacts to movetransversely relative to each other to shear any weld producedtherebetween upon closure thereof.

4. Thetime switch as defined in claim 3 wherein said blade engagingmembers are adapted to be moved to a position wherein said contacts arein a closed position and retained thereby by holding means comprising acam secured to one of said blade engaging members and a switch actuatingmember whereby upon subsequent actuation of said switch actuating memberjust prior to the opening of said contacts said switch actuating membercooperates with said cam to move said one blade engaging member and theblade engaged thereby toward the other blade so as to cause the saidmovement of said contacts transversely relative to one another, and uponfurther movement of said switch actuating member relative to said camsaid blade engaging members are actuated so as to move said blades awayfrom each other to an open contact position.

5. The time switch as defined in claim 4 wherein said switch actuatingmember comprises a pivotally mounted pawl actuated by adjustable switchselectors with the slope of said cam surface being such that the camsurface interferes with themovement of the pawl from said closedposition todrive the cam and the associated blade engagi relative toeach other, said first pair of contacts being mounted on the free endsof said first and second blades and second pair of contacts beingmounted on the free ends of said second and third blades, a pair ofmembers engaging the free ends of said blades and adapted to move atright angles thereto with one of said members engaging the tips of saidfirst and third blades and the other of said members engaging the tipsof said second blade to deflect said blades relative to each other toeither close said first pair of contacts and open said second pair ofcontacts or open said first pair of contacts and close said second pairof contacts, and driving means in cluding a timing motor for moving saidblade engaging means, said driving means operating after closure andprior to opening of either pair of contacts to further defiect saidblades relative to each other to cause the closed contacts to movetransversely relative to each other to shear any weld producedtherebetween upon closure thereof.

(References on fell-swing page) 9 10 References Cited in the file ofthis patent 1,303,161 Cavanagh May 6, 1919 2,142,462 Teeple Jan. 3, 1939UNITED STATES PATENTS 2,270,513 Dettar Jan. 20, 1942 1,048,670 FessendenDec. 31, 1912 2,308,729 Walter Jan. 19, 1943 1,299,457 Gray Apr. 8, 19196 2,690,526 Morrison -2 Sept. 28, 1954

